python - 如何复制嵌套列表中的元素？

Question

我有一个如下所示的嵌套列表:

[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

我想将每个内部列表中的每个元素复制 3 份，并将它们并排放置:

[[1, 1, 1, 2, 2, 2, 3, 3, 3], [4, 4, 4, 5, 5, 5, 6, 6, 6], [7, 7, 7, 8, 8, 8, 9, 9, 9]]

这是我当前的解决方案:

from itertools import repeat

x2 = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

ls = []
for i in x2:
    ls.append([x for item in i for x in repeat(item, 3)])
ls
>>> [[1, 1, 1, 2, 2, 2, 3, 3, 3],
 [5, 5, 5, 6, 6, 6, 7, 7, 7],
 [9, 9, 9, 10, 10, 10, 11, 11, 11],
 [4, 4, 4, 8, 8, 8, 3, 3, 3]]

有什么办法可以让它更快吗？

Answer 1

这是一种解决方案:

ls=[sum([[i]*3 for i in k], []) for k in x2]

>>>print(ls)
[[1, 1, 1, 2, 2, 2, 3, 3, 3], [4, 4, 4, 5, 5, 5, 6, 6, 6], [7, 7, 7, 8, 8, 8, 9, 9, 9]]